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Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions

Qi, Yunliang and Wang, Yingdi and Li, Yanfei and Wang, Jianxin and He, Xin and Wang, Zhi (2019) Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions. Combustion and Flame, 205 . pp. 378-388. ISSN 0010-2180. https://resolver.caltech.edu/CaltechAUTHORS:20190503-124821579

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Abstract

Spark ignition induced super-knock was generated in a rapid compression machine using stoichiometric iso-octane/O_2/N_2 mixture. In addition to the pressure traces, the combustion processes were also recorded using high-speed photography, from which the characteristics of the end-gas auto-ignition were analyzed. The effect of negative temperature coefficient (NTC) on the end-gas auto-ignition was investigated using detailed and reduced reaction mechanisms. The end-gas auto-ignition of diluted methanol/O_2/Ar mixture without NTC behavior was also tested for comparison. The results showed that the end-gas auto-ignition of iso-octane/O_2/N_2 mixture exhibited a two-stage ignition process. During the second ignition stage of the end-gas, two auto-ignition events with very short time interval were sequentially observed in the end-gas region. The first auto-ignition event generated a weak shock wave, and the second one initiated detonation. Both the two auto-ignition events occurred near the wall but at different sites. Due to the heat loss to the wall, the near-wall region is generally considered to be colder than the adiabatic core region, and thus the near-wall auto-ignition of end-gas was usually considered as a result of fuel's NTC behavior. However, in this study the chemical kinetic calculation showed that the evolution of the end-gas almost bypassed the NTC region in the ignition delay-temperature diagram. Furthermore, for the methanol/O_2/Ar mixture the end-gas auto-ignition also started at the very near-wall region. Considering that methanol fuel does not has an NTC behavior, the near-wall auto-ignition of methanol/O_2/Ar mixture should be a result of other factors than NTC. Therefore, it was concluded that NTC might not play a dominant role in the near-wall auto-ignition of the end-gas.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.combustflame.2019.04.014DOIArticle
Additional Information:© 2019 The Combustion Institute. Published by Elsevier Inc. Received 18 January 2018, Revised 5 July 2018, Accepted 7 April 2019, Available online 3 May 2019. This work was supported by National Natural Science Foundation of China (Grant nos. 91541206, 51706121 and 21761142012); and China Postdoctoral Science Foundation (Grant no. 2017T100076).
Group:GALCIT
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China91541206
National Natural Science Foundation of China51706121
National Natural Science Foundation of China21761142012
China Postdoctoral Science Foundation2017T100076
Subject Keywords:Super-knock; End-gas auto-ignition; Detonation; Negative temperature coefficient; Rapid compression machine
Record Number:CaltechAUTHORS:20190503-124821579
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190503-124821579
Official Citation:Yunliang Qi, Yingdi Wang, Yanfei Li, Jianxin Wang, Xin He, Zhi Wang, Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions, Combustion and Flame, Volume 205, 2019, Pages 378-388, ISSN 0010-2180, https://doi.org/10.1016/j.combustflame.2019.04.014. (http://www.sciencedirect.com/science/article/pii/S0010218019301592)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95204
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 May 2019 20:07
Last Modified:03 Oct 2019 21:11

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